1. FIELD OF THE INVENTION
This invention relates to a screw fluid machine for use as a compressor generating a high pressure gas or a cooling-medium-compressing compressor used in a refrigerator or an air conditioner.
2. DESCRIPTION OF THE PRIOR ART
FIG. 1 is a plan view, partly in cross-section, of a conventional type screw fluid machine, and FIG. 2 shows the right-hand side view of the machine of FIG. 1. FIG. 1 however shows the fluid machine having a sound-proof cover removed.
A fluid machine as shown in FIGS. 1 and 2 is a compressor adapted to generate a high pressure gas and consists essentially of an electric drive motor 1, speed-up gear unit or speed change gear unit 2, and a compressor 3. The electric drive motor 1 and speed change gear unit 2 are set up on a common base 5. The compressor 3 consists of a low pressure stage compressor 3l and a high pressure stage compressor 3h, and secured to a casing 6 provided for speed change gear unit 2 through the medium of flanges. The cooler 4 consists of a rear cooler 4a, and an intermediate cooler 4, which is placed in a gas flow path communicating the low pressure stage compressor 3l with the high pressure stage compressor 3h, while the rear cooler 4a is positioned in a gas discharge path of the high pressure stage compressor 3h. The speed change gear unit 2 includes a rotary shaft 9 which is supported by the casing 6 through the medium of bearings 7, 8. A driving gear 10 is secured to the rotary shaft 9 thereon. Two follower or driven gears 11, 12 mesh with the driving gear 10. The follower gear 11 is secured to a rotor shaft 13 for the low pressure stage compressor 3l, while the follower gear 12 is secured to a rotor shaft 14 for the high pressure stage compressor 3h, respectively. One end of the rotary shaft 9 projects from the casing 6 in piercing relation, while a coupling 15 is secured to the projecting end of the rotary shaft 9. The rotary shaft 9 is coupled to the electric drive motor 1 by means of the coupling 15. An inlet side silencer 16 is positioned in an inlet path of the low pressure stage compressor 3l, while a discharge side silencer 17 is placed in a discharge path of the high pressure stage compressor 3h.
With the prior art fluid machine of the arrangement thus described, the low pressure stage compressor 3l, high pressure stage compressor 3h, and speed change gear unit 2 are integrally provided, although these components are provided separately of an intermediate cooler 4i, rear cooler 4a, inlet-side silencer 16, discharge-side silencer 17 or accessories for the compressor 3, such as an oil separator, oil cooler and the like (not shown). The aforesaid accessories are selected for a suitable combination according to the specification required. However, these accessories are provided not integrally, so that the arrangement thereof should be determined for each combination of accessories, and in addition, a space required for accessories is increased, thus failing to reduce the size of a fluid machine. Still furthermore, the compressor 3, i.e., a source of noise is exposed, so that sound stemming from the compressor 3 is directly transmitted to the surrounding, thus posing a noise problem.